German Wi-Fi specialist Spotigo has managed to compile a Wi-Fi radio map of London and other major European cities, enabling it to locate any Wi-Fi device within five metres - and it promises to have the rest of Europe mapped within a year.

Using the Spotigo database any Wi-Fi device can compare the locally-available Wi-Fi hotspots with known locations and work out where it is, offering location information within seconds rather than the minutes it can take to get a GPS fix.

Using hot-spots for location purposes is nothing new - the idea has been around for a decade or so. The problem has always been building up, and maintaining, the database of access points. Spotigo has relationships with wireless ISPs that provide it with 100,000 punters around Europe with GPS-equipped handsets who are logging every access point and location, feeding into the database.

Google Mobile Maps does a similar thing with its MyLocation service, using cellular base stations instead of Wi-Fi, but that makes it accurate to half a mile or so compared to Spotigo's claimed five metres.

In the early days of location-based services many technologies and techniques were suggested, but the ever-decreasing cost of GPS hardware has driven all but a few out of business. Spotigo reckons that the inability to use GPS indoors, and the time it takes to get a fix, will give it the edge. It hints that it'll be embedding the software into a handset from a major manufacturer very soon.

Of course, once Galileo is up and running the problems with satellite systems will be mitigated to some extent, and even GPS keeps improving. So Spotigo is going to have to move fast if it's going to prove that Wi-Fi is a sensible way of locating yourself. ®